sys.stdin.readlines() hangs Python script

Everytime I'm executing my Python script, it appears to hang on this line:

lines = sys.stdin.readlines()

What should I do to fix/avoid this?

EDIT

Here's what I'm doing with lines:

lines = sys.stdin.readlines()
updates = [line.split() for line in lines]

EDIT 2

I'm running this script from a git hook so is there anyway around the EOF?